This invention relates to a switchgear and, more particularly, to a power switchgear such as a circuit interrupter and a contactor.
FIG. 6 illustrates a construction of a distribution panel into which interrupters are incorporated. In the figure, reference numeral 1 is a housing of the distribution panel, 1a s bar compartment defined by partition walls within the housing, 1b is an interrupter compartment, 1c is a cable compartment, 1d is a controller compartment and 1e is a sub-floor space below the interrupter compartment 1b which is supplied with air from the cable compartment 1c on its side and discharge air from the space below the interrupter 7 through a hole (not shown) formed in the ceiling portion of the sub-floor space 1e. 1f is a vent passage for upwardly guiding the air ventilated upwardly from the interrupter 7 and for discharging it outside through an exhaust port (not shown). 2 is a panel-connecting bus bar connected to each of the distributor panels arranged in the depth direction as viewed in the plane of FIG. 6. 3 is an insulator, 4 is a shunt bust bar shunted from the connection bus bar 2, 5 is a bushing, 6 is a main circuit disconnector portion disposed within the bushing, 7 is an interrupter arranged withdrawable in the leftward direction in FIG. 6, 8 is a cable, 9 is a connection conductor connecting the cable 8 to the disconnector portion 6 of the bushing 5 and 10 is a current transformer.
FIG. 7 illustrates one example of the interrupter that can be used in the abovementioned distribution panel disclosed for example in Japanese Patent Laid-Open No. 57-170422. In the figure, 11 is a carriage of the interrupter 7, 12 is a face plate covering the front face of the interrupter 7, 13 is an operating mechanism, 14 is an insulating frame, 14a is a front insulating wall defining a space on the side of the operating mechanism 13, 14b is a side insulating wall defining the side of the insulating frame 14. 15 is a vacuum valve or a switch portion held within the insulating frame 14, 18 are terminal conductors connected to the vacuum valve 15 through a stationary conductor or a flexible conductor 17 and has one end projected from the insulating, frame and 19 are contacts connected to the free ends of the terminal conductors 18 to contact with the main circuit portion 6.
It is to be noted that the operating mechanism 13 is a precise assembly of the precision mechanisms which is required to be always ready for an immediate operation when circuit interruption is required for circuit protection for an extended period of ten to twenty years without being subjected to an inspection or maintenance, so that the operating mechanism is usually enclosed by a metal case in order to eliminate the risk of malfunction of the mechanism due to dust or the like.
Since the conventional interrupter has the construction as above described, the insulating distance A between the operating mechanism 13 and the outer diameter portion of the flange 15a of the vacuum valve 15 which is a live portion of the switchgear could be made small. However, since the insulating frame 14 is open at the side of the distribution panel, the insulating distance between the outer diameter portion of the flange 15a and the ground potential portion of the distribution panel must be made large, so that the distance B from the outer diameter portion of the flange 15a to the tip of the contact must be large, resulting in a large overall length L of the interrupter.
The insulating frame 14 made of an integrally molded material comprises integrally formed three insulating walls but one side must invariably be left open because of the molding method. Heretofore, this open end has been used as the opening for introducing the terminal conductors. Under these conditions, if the insulating distance should be made further smaller, the open end could be closed by an electrically insulating plate. However, since a large amount of heat is generated from the vacuum valve 15 and the conductors 16-18 for an interrupter of a higher rated current, a good ventilation within the insulating fame 14 is necessary to improve the cooling, which requires that the open end of the insulating frame 14 be kept open, obstructing the interrupter to be made small-sized.
Also, since the operating mechanism is enclosed within a metal case to prevent the entry of the dust or the like to ensure a long term reliable precision operation of the operating mechanism, when the open end of the insulating frame is used on the operating mechanism, the insulating distance at the open end of the insulating frame will become disadvantageously large.